When Andy Burnham sought the UK premiership in the summer, he corralled two finance heavyweights to bolster his credentials — Jim O’Neill, an ex-Conservative minister and Goldman Sachs Group Inc. alumnus, and former Bank of England Chief Economist Andy Haldane. As he marks 100 days in office today and ahead of his first budget on Wednesday, Burnham would do well to heed his erstwhile advisers’ warnings that Britain’s central problems — weak growth, spiraling public spending and soaring debt — remain unaddressed.

The pair had come into Burnham’s orbit during his successful tenure as mayor of Manchester from 2017, working with him to attract the private finance that turned a tired, dilapidated Northern city into a boomtown. As he campaigned to become prime minister, Burnham enlisted their bona fides to reassure investors spooked by his infamous declaration that the economy shouldn’t be “in hock to the bond markets.”Despite expectations, neither O’Neill nor Haldane entered 10 Downing Street alongside Burnham in July.

Recollections may vary about the reasons: Both Haldane and O’Neill insist they weren’t spurned, but decided they didn’t want to give up other projects in order to work in government. Whatever happened, both appeared to cool on Burnham during his first months in office; Haldane in particular swiftly became a not-so-friendly critic, describing economics as the PM’s blind spot.

Privately, some close to government accuse Haldane of sour grapes, adding that he’s developed a liking for the media attention he garners from his colorful salvos, such as his musing that the new administration may be a “traditional tax-and-spend socialist government with better TikTok videos.”In the past week alone, Haldane has advised the government to put on a “chastity belt” with regard to spending, has claimed Britain is “close to being taxed out and maxed out,” and has said Burnham can’t “vibe-code” his way to growth.

O’Neill has been more circumspect. Having advised Chancellor of the Exchequer John Healey to ignore calls from left-wing Labour lawmakers for wealth taxes and describing the PM’s ambition to achieve “growth in every postcode” as “lunacy,” in recent weeks he seems to have regained the chancellor’s ear. Healey appears to have listened to O’Neill’s warning not to equalize capital gains and income taxes, a proposal supported by cabinet colleagues including Defence Secretary Wes Streeting and First Secretary Louise Haigh.

And O’Neill approves of a widely anticipated plan to include less fiscal headroom in the budget than Healey’s predecessor Rachel Reeves reserved last year, perhaps down to as little as £12 billion ($16 billion).

It’s good that O’Neill appears to be back in the fold. But whatever the bad blood between them, Healey would do well to listen to Haldane too.

The expectation is that this will be a small-scale budget, designed to soothe the markets and maintain confidence in this still newish administration. As my colleague Mihir Sharma has written, Healey is seeking “not repair but reassurance.”But given the scale of Burnham’s rhetoric on taking office — his promise to lead a transformative government ending decades of economic malaise — incremental moves announced in pre-budget briefings such as trimming red tape for small businesses and protecting poorer pensioners from income tax will fall woefully short.

Longer term, the chancellor needs to tackle the high government borrowing that makes everything else so much harder, from meeting the government’s defense-spending targets to funding Burnham’s laudably ambitious proposal to launch a comprehensive national care service. As Haldane has argued, reducing a debt pile that recently surpassed £3 trillion requires welfare reform on a scale that lawmakers in Burnham’s left-of-center Labour party will find uncomfortable — remember it was his predecessor Keir Starmer’s inability to force substantial cuts through Parliament that ultimately led to his demise. Those pressures still exist: The UK spends more servicing its debt than it does on education.

Wednesday’s statement is already being described by some as a "budget" that kicks many of the economic challenges down the road. Some more details about where the money will be found for No. 10’s pet projects, including raising defense spending to 3.5% of gross domestic product, may come in a so-called 10-year plan that’s due in a few weeks, or as part of a spending review penciled in for the spring. But delay can’t continue indefinitely; at some point the chancellor will have to come up with the goods, or risk the current government proving yet another case of politicians promising big and delivering small.

Healey and Burnham should start listening to their truculent former adviser. Haldane is right: The government must cut spending and chart a course to reducing Britain’s indebtedness to achieve the transformation the prime minister has promised.